question_answer

Law of dominance explained by Mendel has its basis on which type of cross?

A)  Monohybrid cross  

B)  Dihybrid cross

C)  Reciprocal cross   

D)  None of these

Correct Answer: A

Solution :

 Law of dominance (explained by Mendel) is based on monohybrid cross. Law of dominance states that when two different allelomorphic forms (genes) are present in an organism,  only  one  expresses  itself in \[{{\text{F}}_{\text{1}}}-\] generation, which is called dominant gene while the other which does not show its effect and remains marked is called recessive gene. When a cross is performed between two individuals taking a single contrasting character at a time, it is called a monohybrid cross. For example, the character height in pea plant has two alleles T and t. T exhibits tallness whereas t exhibits dwarfness. When a pure tall (TT) pea plant is crossed with a pure dwarf (tt) plant, in the \[{{\text{F}}_{\text{1}}}-\]generation hybrid (heterozygous) Tt is obtained which is tall due to the presence of allele T. This shows that tallness is dominant over dwarfness which remain unexpressed in generation.